RT8298 RICHTEK | Alldatasheet
Document overview
- Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
- PDF pages: 18
Technical content
Features
zzzzz 4.5V to 24V Input Voltage Range zzzzz 6A Output Current zzzzz 45mΩΩΩΩΩ Internal High Side N-MOSFET zzzzz Current Mode Control zzzzz 600kHz Switching Frequency zzzzz Adjustable Output from 0.8V to 15V zzzzz Up to 95% Efficiency zzzzz Internal Compensation zzzzz Stable with Ceramic Capacitors zzzzz Synchronous External Clock : 300kHz to 1.5MHz zzzzz Cycle-by-Cycle Current Limit zzzzz Input Under Voltage Lockout zzzzz Output Under Voltage Protection zzzzz Power Good Indicator zzzzz Thermal Shutdown Protection z RoHS Compliant and Halogen Free
Applications
z Point of Load Regulator in Distributed Power System z Digital Set top Boxes z Personal Digital Recorders z Broadband Communications z Flat Panel TVs and Monitors RT8298 VIN CIN VIN VCC CVCC PGOODPower Good EN/SYNC FB BG SW BOOT CBOOT L VOUT COUT R2Chip Enable GND
DS8298-01 November 2011www.richtek.com RT8298 Copyright 2011 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation.©
Ordering Information
Note : Richtek products are : \ RoHS compliant and compatible with the current require- ments of IPC/JEDEC J-STD-020. \ Suitable for use in SnPb or Pb-free soldering processes. Marking Information 04 YM DNN RT8298 ZSPYMDNN RT8298ZQW RT8298ZSP 04 : Product Code YMDNN : Date Code RT8298ZSP : Product Number YMDNN : Date Code Pin Configurations (TOP VIEW) WDFN-14L 4x3 FB PGOOD VIN VIN GND BG VCC SW BOOT EN/SYNC VIN SW NC SW GND 1578 SOP-8 (Exposed Pad) SW BOOT VCC BG VIN EN/SYNC GND FB GND 4 5 RT8298 Package Type QW : WDFN-14L 4x3 (W-Type) SP : SOP-8 (Exposed Pad-Option 2) Lead Plating System Z : ECO (Ecological Element with Halogen Free and Pb free)
DS8298-01 November 2011 www.richtek.com RT8298 Copyright 2011 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation.© Functional Pin Description Pin No. WDFN-14L 4x3 SOP-8 (Exposed Pad) Pin Name Pin Function 1 6 FB Feedback Input. This pin is connected to the converter output. It is used to set the output of the converter to regulate to the desired value via an external resistive divider. The feedback reference voltage is 0.808V typically. 2 -- PGOOD Power Good Indicator with Open Drain. (for RT8298ZQW only) A 100kΩ pull-high resistor is needed. The output of this pin is pulled to low when the FB is lower than 0.75V; otherwise it is high impedance. 3 7 EN/SYNC Enable or External Frequency Synchronization Input. A logic-high (2V < EN < 5.5V) enables the converter; a logic-low forces the IC into shutdown mode reducing the supply current to less than 3μA. For external frequency synchronization operation, the available frequency range is from 300kHz to 1.5MHz. 4, 5, 6 8 VIN Power Input. The available input voltage range is from 4.5V to 24V. A 22 μF or larger input capacitor is needed to reduce voltage spikes at the input. 7 -- NC No Internal Connection. 8, 9, 10 1 SW Switching Node. Output of the internal high side MOSFET. Connect this pin to external low-side N-MOSFET, inductor and bootstrap capacitor. 11 2 BOOT Bootstrap for High side Gate Driver. Connect a 1 μF ceramic capacitor between the BOOT pin and SW pin. 12 3 VCC BG Driver Bias Supply. Decouple with a 1 μF X5R/X7R ceramic capacitor between the VCC pin and GND. 13 4 BG Gate Driver Output. Connect this pin to the gate of the external low-side N-MOSFET. 14, 15 (Exposed Pad) 9 (Exposed Pad) GND Ground. The exposed pad must be soldered to a large PCB and connected to GND for maximum thermal dissipation.
DS8298-01 November 2011www.richtek.com RT8298 Copyright 2011 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation.© Function Block Diagram Operation The RT8298 is a synchronous high voltage Buck Converter that can support the input voltage range from 4.5V to 24V and the output current can be up to 6A. The RT8298 uses a constant frequency, current mode architecture. In normal operation, the high side N-MOSFET is turned on when the Switch Controller is set by the oscillator (OSC) and is turned off when the current comparator resets the Switch Controller. While the N-MOSFET is turned off, the external low side N-MOSFET is turned on by BG Driver with 5V driving voltage from Internal Regulator (V CC) until next cycle begins. High side MOSFET peak current is measured by internal RSENSE. The Current Signal is where Slope Compensator works together with sensing voltage of RSENSE. The error amplifier EA adjusts COMP voltage by comparing the feedback signal (V FB) from the output voltage with the internal 0.808V reference. When the load current increases, it causes a drop in the feedback voltage relative to the reference, the COMP voltage then rises to allow higher inductor current to match the load current. UV Comparator : If the feedback voltage (V FB) is lower than threshold voltage 0.4V, the UV Comparator's output will go high and the Switch Controller will turn off the high side MOSFET. The output under voltage protection is designed to operate in Hiccup mode. Oscillator (OSC) : The internal oscillator runs at nominal frequency 600kHz and can be synchronized by an external clock in the range between 300kHz and 1.5MHz from EN/ SYNC pin. PGOOD Comparator : This function is available for RT8298ZQW only. When the feedback voltage (V FB) is higher than threshold voltage 0.75V, the PGOOD open drain output will be high impedance. Enable Comparator : Internal 5kΩ resistor and Zener diode are used to clamp the input signal to 3V. A 1.7V reference voltage is for EN logic-high threshold voltage. The EN pin can be connected to VIN through a 100k Ω resistor for automatic startup. Foldback Control : When V FB is lower than 0.7V, the oscillation frequency will be proportional to the feedback voltage. Soft-Start (SS) : An internal current source (6nA) charges an internal capacitor (15pF) to build the soft-start ramp voltage (V SS). The VFB voltage will track the internal ramp voltage during soft-start interval. The typical soft-start time is 2ms. Internal Regulator Enable Comparator EN/SYNC 1.7V 5k 3V VIN OSC Foldback Control 1pF 54pF 300k EA0.808V UV Comparator Current Comparator 0.4V FB BOOT 45m SW PGOOD GND Current Sense Amplifier Slope Compensator PGOOD Comparator BG Driver BG Switch Controller 0.75V VCC RSENSE VCC OTP COMP 6nA 15pF VCC VSS VCC Current Signal
DS8298-01 November 2011 www.richtek.com RT8298 Copyright 2011 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation.© Recommended Operating Conditions (Note 4) Absolute Maximum Ratings (Note 1) z Power Dissipation, PD @ TA = 25°C z Package Thermal Resistance (Note 2) z ESD Susceptibility (Note 3) Parameter Symbol Test Conditions Min Typ Max Unit Shutdown Supply Current V EN = 0V -- 1 -- μA Supply Current V EN = 3V, VFB = 1V -- 0.9 -- mA Feedback Reference Voltage V REF 4.5V ≤ VIN ≤ 24V 0.796 0.808 0.82 V Feedback Current I FB V FB = 0.8V -- 10 -- nA High-Side Switch On Resistance R DS(ON) -- 45 -- m Ω High-Side Switch Current Limit BOOT − SW = 4.8V -- 10 -- A Oscillation Frequency f OSC1 -- 600 -- kHz Short Circuit Oscillation Frequency f OSC2 V FB = 0V -- 190 -- kHz Maximum Duty Cycle D MAX V FB = 0.6V -- 90 -- % Minimum On-Time t ON V FB = 1V -- 100 -- ns Input Under Voltage Lockout Threshold V UVLO 4 4.2 4.4 V Input Under Voltage Lockout Threshold Hysteresis ΔVUVLO -- 400 -- mV Logic-High V IH 2 -- 5.5 EN Threshold Voltage Logic-Low V IL -- -- 0.4 V (VIN = 12V, TA = 25°C, unless otherwise specified)
Electrical Characteristics
DS8298-01 November 2011www.richtek.com RT8298 Copyright 2011 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation.© Parameter Symbol Test Conditions Min Typ Max Unit Sync Frequency Range fSync 0.3 -- 1.5 MHz EN Turn-Off Delay t OFF -- 10 -- μs EN Pull Low Current V EN = 2V -- 1 -- μA Thermal Shutdown T SD -- 150 -- °C Thermal Shutdown Hysteresis ΔTSD -- 20 -- °C Power Good Threshold Rising -- 0.75 -- V Power Good Threshold Hysteresis -- 40 -- mV Power Good Pin Level PGOOD Sink 10mA -- -- 0.125 V BG Driver Bias Supply Voltage V CC 4.5 5 -- V Gate Driver Sink Impedance R Sink -- 0.9 -- Ω Gate Driver Source Impedance R Source -- 3.3 -- Ω Note 1. Stresses beyond those listed “Absolute Maximum Ratings ” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may affect device reliability. Note 2. θ JA is measured at T A = 25 °C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is measured at the exposed pad of the package. Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions.
Table 1. Recommended Component Selection
2 PGOODPower Good
DS8298-01 November 2011www.richtek.com RT8298 Copyright 2011 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation.© Output Voltage vs. Temperature 3.20 3.22 3.24 3.26 3.28 3.30 3.32 3.34 3.36 3.38 3.40 -50 -25 0 25 50 75 100 125 Temperature (°C) Output Voltage (V) VIN = 12V, VOUT = 3.3V, IOUT = 0A Output Voltage vs. Output Current 3.20 3.22 3.24 3.26 3.28 3.30 3.32 3.34 3.36 3.38 3.40 Output Current (A) Output Voltage (V) VIN = 6V VIN = 12V VIN = 24V VOUT = 3.3V Typical Operating Characteristics Switching Frequency vs. Input Voltage 550 560 570 580 590 600 610 620 630 640 650 4 6 8 1 01 21 41 61 82 02 22 4 Input Voltage (V) Switching Frequency (kHz) 1 VOUT = 3.3V, IOUT = 0A Efficiency vs. Output Current 100 0123456 Output Current (A) Efficiency (%) VOUT = 3.3V VIN = 6V VIN = 12V VIN = 24V Output Voltage vs. Input Voltage 3.27 3.28 3.29 3.30 3.31 3.32 3.33 4 6 8 1 01 21 41 61 82 02 22 4 Input Voltage (V) Output Voltage (V) VIN = 4.5V to 24V, V OUT = 3.3V, IOUT = 0A Switching Frequency vs. Temperature 550 560 570 580 590 600 610 620 630 640 650 -50 -25 0 25 50 75 100 125 Temperature (°C) Switching Frequency (kHz) 1 VIN = 12V, VOUT = 3.3V, IOUT = 0A
DS8298-01 November 2011 www.richtek.com RT8298 Copyright 2011 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation.© Current Limit vs. Temperature 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 -50 -25 0 25 50 75 100 125 Temperature (°C) Current Limit (A) VIN = 12V, VOUT = 3.3V Time (2.5ms/Div) Power On from VIN VIN = 12V, VOUT = 3.3V, IOUT = 6A VOUT (2V/Div) VIN (5V/Div) IL (5A/Div) Time (1 μs/Div) Output Ripple Voltage VOUT (10mV/Div) VSW (10V/Div) IL (5A/Div) VIN = 12V, VOUT = 3.3V, IOUT = 6A Time (1 μs/Div) Output Ripple Voltage VOUT (10mV/Div) VSW (10V/Div) IL (2A/Div) VIN = 12V, VOUT = 3.3V, IOUT = 3A Time (250 μs/Div) Load Transient Response VOUT (100mV/Div) IOUT (5A/Div) VIN = 12V, VOUT = 3.3V, IOUT = 0A to 6A Time (250 μs/Div) Load Transient Response VOUT (100mV/Div) IOUT (5A/Div) VIN = 12V, VOUT = 3.3V, IOUT = 3A to 6A
DS8298-01 November 2011www.richtek.com RT8298 Copyright 2011 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation.© Time (5ms/Div) Power Off from EN VOUT (2V/Div) VEN (5V/Div) IL (5A/Div) VIN = 12V, VOUT = 3.3V, IOUT = 6A Time (500ns/Div) External SYNC VLX (10V/Div) Clock (5V/Div) IL (5A/Div) VIN = 12V, VOUT = 3.3V, IOUT = 6A, Clock = 800kHz VOUT (5V/Div) Time (2.5ms/Div) Power On from EN VOUT (2V/Div) VEN (5V/Div) IL (5A/Div) VIN = 12V, VOUT = 3.3V, IOUT = 6A Time (5ms/Div) Power Off from VIN VOUT (2V/Div) VIN (5V/Div) IL (5A/Div) VIN = 12V, VOUT = 3.3V, IOUT = 6A
Table 2. External N-MOSFET Selection and decreases with higher inductance. requires a large inductor to achieve this goal. see Table 3 for the inductor selection reference. Table 3. Suggested Inductors for Typical trapezoidal current at the source of the high side MOSFET. deviations do not offer much relief. meet size or height requirements in the design.
Table 4. Suggested Capacitors for CIN and COUT ringing that would indicate a stability problem. the RT8298, the maximum junction temperature is 125°C. 51-7 four-layer thermal test board. ESR and RMS current handling requirement. IN large enough to damage the part. capacitor, please refer to Table 4 for more details. for COUT selection to ensure that the control loop is stable. response as described in a later section.
Figure 8. Derating Curves for RT8298 Package \` Connect feedback network behind the output capacitors. and Figure 10 for reference.
DS8298-01 November 2011 www.richtek.com RT8298 Copyright 2011 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation.© Outline Dimension Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 0.700 0.800 0.028 0.031 A1 0.000 0.050 0.000 0.002 A3 0.175 0.250 0.007 0.010 b 0.180 0.300 0.007 0.012 D 3.900 4.100 0.154 0.161 D2 3.250 3.350 0.128 0.132 E 2.900 3.100 0.114 0.122 E2 1.650 1.750 0.065 0.069 e 0.500 0.020 L 0.350 0.450 0.014 0.018 W-Type 14L DFN 4x3 Package
DS8298-01 November 2011www.richtek.com RT8298 Richtek Technology Corporation 5F, No. 20, Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnish ed by Richtek is believed to be accurate and reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringeme nts of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of R ichtek or its subsidiaries. A BJ F H M C D I Y X EXPOSED THERMAL PAD (Bottom of Package) 8-Lead SOP (Exposed Pad) Plastic Package Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 4.801 5.004 0.189 0.197 B 3.810 4.000 0.150 0.157 C 1.346 1.753 0.053 0.069 D 0.330 0.510 0.013 0.020 F 1.194 1.346 0.047 0.053 H 0.170 0.254 0.007 0.010 I 0.000 0.152 0.000 0.006 J 5.791 6.200 0.228 0.244 M 0.406 1.270 0.016 0.050 X 2.000 2.300 0.079 0.091 Option 1 Y 2.000 2.300 0.079 0.091 X 2.100 2.500 0.083 0.098 Option 2 Y 3.000 3.500 0.118 0.138